This post is for administrators only.
Groups topics can be defined to classify groups.
This can be done from the Groups administration section, by clicking Manage topics.
When topics are created, the administrators or the groups admins can assign a topic to a group. This can be done either from the topics management page in the Groups administration section, or from the groups panel, Information & privacy.
When groups are assigned to topics, they are sorted by topics in the groups directory. They are also sorted by topics in the navigation side bar unless users have disabled this in their preferences.